Hi Chaitanya,<br><br>thanks, i'll try that when I get back to it tomorrow. <br><br>But: I guess I will have to add -vrtnodata aswell, hopefully it will add pixels to the mask ?<br><br>I have already converted all the source TIFFs to lossless compressed GeoTiff (which don't <br>
produce undesired JPEG artifacts), and made a VRT that tiles them together using -vrtnodata <br>(suggestion from Michael Smith). <br><br>This works well, but having compression with JPEG + mask would be nice. Some of the files<br>
are still quite large (including gdaladdo overviews)<br><br>-- Oyvind<br><br><br><br><div class="gmail_quote">On Tue, Apr 3, 2012 at 7:35 PM, Chaitanya kumar CH <span dir="ltr"><<a href="mailto:chaitanya.ch@gmail.com">chaitanya.ch@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Oyvind,<div><br></div><div>One easy method is to create a vrt file with an alpha band for the original tiff. You can use this to create a compressed raster file that will be </div>
<div>transparent at nodata pixels.<br><br>
<font face="'courier new', monospace">gdalbuildvrt -addalpha</font></div><div><br></div><div><a href="http://www.gdal.org/gdalbuildvrt.html" target="_blank">http://www.gdal.org/gdalbuildvrt.html</a><br><br><div class="gmail_quote">
<div><div class="h5">
On Tue, Apr 3, 2012 at 5:26 PM, Oyvind Idland <span dir="ltr"><<a href="mailto:oyvind.idland@gmail.com" target="_blank">oyvind.idland@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div><div class="h5">
Hello,<br><br><br>I got one problem: I have a bunch of uncompressed TIFF tiles, which I am converting to compressed GeoTiff. I would<br>like to mask away the rgb(0,0,0) values.<br><br>However, when I use NODATA on my VRT dataset, there are JPEG artifacts around the edges when rendering.<br>
<br>Is it possible to generate a transparency mask based on NDATA before compressing, or is there any other/better way of <br>doing this ?<br><br>thanks,<br><br>- oyvind<br>
<br>
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<br clear="all"><div><br></div>-- <br>Best regards,<br>Chaitanya kumar CH.<br>
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